EXT4 group descriptors corrupted

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1

I have a second HD partitioned and formated to EXT4, the whole capacity. It was mounted to a directory in my home folder
I’m getting an error that it cannot be mounted.

Running “dmesg | tail” i get this: (rigt now the HD is connected to the computer using a USB adaptor)


laptop:~> dmesg | tail
  375.821495] sd 9:0:0:0: [sdb] Write Protect is off
  375.821505] sd 9:0:0:0: [sdb] Mode Sense: 00 38 00 00
  375.821512] sd 9:0:0:0: [sdb] Assuming drive cache: write through
  375.823508] sd 9:0:0:0: [sdb] Assuming drive cache: write through
  375.823519] sdb: detected capacity change from 0 to 320072933376
  375.832768]  sdb: sdb1
  375.834621] sd 9:0:0:0: [sdb] Assuming drive cache: write through
  375.834632] sd 9:0:0:0: [sdb] Attached SCSI disk
  376.360004] EXT4-fs (sdb1): ext4_check_descriptors: Block bitmap for group 1 not in group (block 1026)!
  376.360480] EXT4-fs (sdb1): group descriptors corrupted!

What can i do to save the data ?

2

Have you tried to fsck the drive?

If not something like this as root may fix things: fsck.ext4 -y -f /dev/sdb1

It may take quite a while to run so just let it do it’s thing

Incidentally if you have the drive as a persistent mount wouldn’t it be better to use the drive as internal rather than usb?

Personally I wouldn’t persistently mount a usb drive as they just aren’t reliable enough and if anything ‘breaks’ the usb connection while it’s being written like the lead getting slightly dislodged for example, you can end up with filesystem corruption, and it very much looks like that’s what might have happened in your case

3

That is the situation on my system, but because i had a total system meltdown, i’m trying to access the data on the HD from a laptop, hence the USB adaptor.

I will check the command you suggested.

4

If fsck finds and fixes errors, which it’s usually pretty good at doing unless a drive is physically failing you’ve a good chance of getting at your data after it’s finished running

5

OK, I ran the fsck command. it finished and apparently it was fixed. But when i mount the drive “mount /dev/sdb1 ~/Disk2” all i see is an empty drive.

If i run ‘df -h /dev/sdb1’ i get:

> df -h /dev/sdb1
Filesystem Size Used Avail Use% Mounted on
/dev/sdb1 294G 185G 94G 67% /home/ronen/Disk2

Which means there are files on that drive (or at least the file system thinks there are files).
What can i do to retrieve them ?

thank you

6

Remember that the filesystem objects still retain their ownership info even though the filesystem is mounted under your home. So you may need to access them as root.

7

I am the owner of those files. before the crash, the drive was mounted to the directory under my home, using the same user name

8

I think i know what happened. the recovered files are in the lost+found folder. if i open the folder as root i can see them.

now… i need to know how to recover them…

9

Unfortunately you just have to try to guess the original name of the file from the contents. The “file” command can help you guess what it might be.

10

What do you think about these instructions ?

11

On 2011-08-02 22:46, Argoson wrote:

> What do you think about these ‘instructions’
> (http://tinyurl.com/3sgayxw) ?

I don’t see how he figured out that such file number was such name - unless
the corrupted names were only the first level.

It seems that ext4 can get royally corrupted. That was the prerogative or
reiserfs… progress :frowning:

–
Cheers / Saludos,

Carlos E. R.
(from 11.4 x86_64 “Celadon” at Telcontar)

12

The numbers are just for the top level folders. inside the files retain their original names, so i managed to recover what i needed easily. i’m very happy.

I agree about how EXT4 corrupts. the last crash i had i was surprised how easily the file system got unusable. In that matter - at least in my experience - windows’ NTFS (and even older FAT/FAT32) is much stable. the OS can go bonkers but you can just take out the HD and recover the files easily.

13

On 2011-08-03 19:16, Argoson wrote:
> I agree about how EXT4 corrupts. the last crash i had i was surprised
> how easily the file system got unusable. In that matter - at least in my
> experience - windows’ NTFS (and even older FAT/FAT32) is much stable.
> the OS can go bonkers but you can just take out the HD and recover the
> files easily.

Ext4 is relatively new, you can use ext3 instead.

–
Cheers / Saludos,

Carlos E. R.
(from 11.4 x86_64 “Celadon” at Telcontar)

14

so you recommend that i format to ext3 when installing a new system or formating a partition , instead of ext4 ?

15

Ext4’s been released since Dec 2008. I’ve used it for a couple of years with no issues. But maybe for some people that’s still too short.

Maybe it’s less resistant to directory loss due to bad blocks, but I think there are more serious things at stake when you have bad blocks.

16

On 2011-08-05 02:56, Argoson wrote:

> so you recommend that i format to ext3 when installing a new system or
> formating a partition , instead of ext4 ?

No, I can’t recommend that, you make your own choices. Me, I do not use
ext4 on important things yet. You consider the advantages and disadvantages
and risks, and choose.

–
Cheers / Saludos,

Carlos E. R.
(from 11.4 x86_64 “Celadon” at Telcontar)

17

Hello, I’m having the same problem.I am getting grub rescue when booting from hard drive. I tried ls commands, but wasn’t able to access (hd0,msdos1) etc. I am now using usb 12.04 using terminal. I tried fsck and comes up with emergency help screen. One option is -p (automatic repair) tried this and came back (command not found)

18

On 2014-01-18 06:56, moonman555 wrote:

> Hello, I’m having the same problem.I am getting grub rescue when booting
> from hard drive.

If you are getting the error at grub prompt, it is not the same problem.
It is better, I think, that you create a new thread with details,
instead of tagging on a thread that is 3 years old.

–
Cheers / Saludos,

Carlos E. R.
(from 12.3 x86_64 “Dartmouth” at Telcontar)